Among infrared light sensors capable of sensing an infrared light, a thermo electric conversion element is well known. Such a thermo electric conversion element detects and converts an infrared light into heat using an infrared light absorption film, thereby detecting temperature of the heat, as discussed in Japanese Patent Registration No. 2663612.
Other than the infrared light sensor, a sensor using an electric field effect transistor is typically used. Such a sensor generates a voltage (PTAT: Proportional To Absolute Temperature) in proportion to an absolute temperature, as discussed in Japanese Patent Application Laid Open No. 2001-284464.
When temperature is to be detected, with high precision, using infrared light, a thermistor (TM) is typically used in addition to a thermopile provided in an infrared light sensor section to detect an ambient temperature of the infrared light sensor.
An analog signal processing circuit is necessarily used to amplify and compare two signals output from the infrared light sensor section and the thermistor (TM).
Further, the temperature sensor detects and determines temperature when the sensor counterbalances with an ambient temperature, as discussed in the Japanese Patent Application Laid Open NO. 2001-284464.
However, a problem remains unsolved in background devices.